All the following are examples of atrophy except
A. skeletal muscle, following transection of its motor neuron
B. skeletal muscles, following long-term immobilization of the broken extremity in a cast
C. ovary following hypophysectomy
D. endometrium following long-term administration of estrogen
Ans.
D.
All answers except for D are examples of atrophy. Atrophy of skeletal muscles
can result from a loss of innervation due to spinal cord or peripheral nerve
trauma. Inactivity, as is often seen following the long-term immobilization of
an extremity in a cast, has the same effect. Hypophysectomy is accompanied by
atrophy of the thyroid, adrenal cortex, and ovary, which are all organs that
depend on stimulation by pituitary trophic hormones. The brain atrophies with
advancing age. Estrogen exerts trophic
effects on the endometrium, causing hyperplasia rather than atrophy. Endometrial
atrophy occurs following ovariectomy or after the menopause, when the
ovaries no longer produce estrogen.
